In general, the laser welding has been employed in many cases for bonding of electronic parts and the like, because the thermal influence to peripheral portions of the part can be alleviated.
The present applicant has provided a solid laser device by which the processing of a work can be carried out under optimal processing conditions by conducting the waveform control higher in accuracy and rich in variety by realizing the fine or rapid pulse control, as disclosed in Patent Document 1, i.e., Japanese Patent Application Laid-open No. 8-321651.
Works to be welded by a laser welding process are beginning to be extended to micro parts with the development of the reduction in size of instruments and the micrometric reduction in size of parts, as represented by recent clocks, mobile phones, medical instruments and the like.
In many conventional pulse laser welding system, an output energy was set in a range of 5 to 100 joule (J)/pulse, and a laser pulse width was set in a range of 0.5 to 20 ms. If a stainless work is subjected to a fine laser spot welding by such a conventional laser welding system, the following disadvantage is encountered: a minimal welding nugget diameter is on the order of 100 μm (400 to 800 μm), and a maximal penetration depth is restricted to the order of 100 μm.
On the other hand, a welding quality desired with the reduction in size of current parts is such that a welding nugget diameter is equal to or smaller than 100 μm, and a penetration depth is at least equal to or larger than 200 μm, i.e., the same degree as that in the prior art from the relationship to a plate thickness and a welding strength.